Macrophage-specific PPARgamma controls alternative activation and improves insulin resistance - PubMed (original) (raw)

. 2007 Jun 28;447(7148):1116-20.

doi: 10.1038/nature05894. Epub 2007 May 21.

Affiliations

Macrophage-specific PPARgamma controls alternative activation and improves insulin resistance

Justin I Odegaard et al. Nature. 2007.

Abstract

Obesity and insulin resistance, the cardinal features of metabolic syndrome, are closely associated with a state of low-grade inflammation. In adipose tissue chronic overnutrition leads to macrophage infiltration, resulting in local inflammation that potentiates insulin resistance. For instance, transgenic expression of Mcp1 (also known as chemokine ligand 2, Ccl2) in adipose tissue increases macrophage infiltration, inflammation and insulin resistance. Conversely, disruption of Mcp1 or its receptor Ccr2 impairs migration of macrophages into adipose tissue, thereby lowering adipose tissue inflammation and improving insulin sensitivity. These findings together suggest a correlation between macrophage content in adipose tissue and insulin resistance. However, resident macrophages in tissues display tremendous heterogeneity in their activities and functions, primarily reflecting their local metabolic and immune microenvironment. While Mcp1 directs recruitment of pro-inflammatory classically activated macrophages to sites of tissue damage, resident macrophages, such as those present in the adipose tissue of lean mice, display the alternatively activated phenotype. Despite their higher capacity to repair tissue, the precise role of alternatively activated macrophages in obesity-induced insulin resistance remains unknown. Using mice with macrophage-specific deletion of the peroxisome proliferator activated receptor-gamma (PPARgamma), we show here that PPARgamma is required for maturation of alternatively activated macrophages. Disruption of PPARgamma in myeloid cells impairs alternative macrophage activation, and predisposes these animals to development of diet-induced obesity, insulin resistance, and glucose intolerance. Furthermore, gene expression profiling revealed that downregulation of oxidative phosphorylation gene expression in skeletal muscle and liver leads to decreased insulin sensitivity in these tissues. Together, our findings suggest that resident alternatively activated macrophages have a beneficial role in regulating nutrient homeostasis and suggest that macrophage polarization towards the alternative state might be a useful strategy for treating type 2 diabetes.

PubMed Disclaimer

Figures

Figure 1

Figure 1

PPARγ regulates alternative macrophage activation. a, Decreased induction of arginase activity by IL-4 in PPARγ null macrophages. BMDM from control and Mac-PPARγ KO mice were stimulated with IL-4 (10ng/ml) for 24 or 48 hours prior to quantification of cell-associated arginase activity. b, Activation of arginase I promoter by PPARγ/RXR heterodimers. c, PPARγ is required for suppression of IL-6 production in alternatively activated macrophages. Macrophages pre-treated with IL-4 (10 ng/ml) for 24 hours were subsequently stimulated with LPS (5 ng/ml) for 6 hours (TNFα) or 24 hours (IL-6). d, PPARγ is required for macrophage oxidative metabolism. Fatty acid oxidation rates were quantified in control, PPARδ null and PPARγ null BMDMs 96 hours after stimulation with IL-4. e-f, IL-4 fails to induce mitochondrial biogenesis in PPARγ deficient macrophages, as measured by (e) Mito Tracker Green and (f) CytC and VDAC1 protein levels. Equivalent loading was confirmed by immunoblotting for β-actin. Rosiglitazone (Rosi).

Figure 2

Figure 2

Mac-PPARγ KO mice are less susceptible to infection by Leishmania major. a, Footpad swelling in control and Mac-PPARγ KO mice after infection with L. major (n=5/genotype). b, Decreased necrosis in footpads of Mac-PPARγ KO mice.

Figure 3

Figure 3

Alterations in adipose tissue mass and function in Mac-PPARγ KO mice. a, Weight gain of control and Mac-PPARγ KO mice on a HFD. Arrow denotes period when mice were fasted for glucose and insulin tolerance tests. b, Body composition as determined by DEXA (n=5/genotype). c, Q-PCR analyses of gonadal adipose tissue gene expression. Relative transcript levels of genes involved in adipocyte differentiation and function. Lpl, lipoprotein lipase; Cd36, fatty acid translocase; Slc27a1, fatty acid transporter 1; Slc2a4, glucose transporter 4; Fabp4, fatty acid binding protein 4; Lipe, hormone sensitive lipase; Fasn, fatty acid synthase; Acaca, acetyl-Coenzyme A carboxylase a; Acox1, acyl-Coenzyme A oxidase 1; Cpt1a, carnitine palmitoyltransferase 1a; Acadm and Acadl, medium- and long-chain acyl-CoA dehydrogenase; Adipoq, adiponectin; Srebf1, sterol regulatory element binding factor 1c. d, Co-culture of macrophages with adipocytes decreases insulin-stimulated glucose uptake. BMDMs from control or Mac-PPARγ KO mice were co-cultured with differentiated 3T3-L1 adipocytes for 48 hours. 2-deoxyglucose uptake was assessed 30 minutes after stimulation with insulin. e, Q-PCR analyses of macrophage gene expression in WAT from control and Mac-PPARγ KO mice. Emr1, F4/80; Cd68, macrosialin; Arg1, arginase I; Mrc1, mannose receptor; Clec7a, dectin-1; Retnla, resistin like alpha; Nos2, inducible nitric oxide synthase; IL-6, interleukin-6. f-g, Macrophage content of epididymal adipose tissue. Representative sections of epididymal fad pads stained with F4/80 (Emr1) antibody (f). Fraction of ATMs is equal to F4/80-stained cells/total cells counted in the fields (g), and statistically analyzed using the paired t-test.

Figure 4

Figure 4

Impaired glucose homeostasis in high fat fed male Mac-PPARγ KO mice. a, Oral glucose tolerance tests (1 g/kg) in male mice after 19 weeks of feeding the HFD (n=5/genotype). b, Insulin tolerance test. Obese mice were fasted for 4 hours prior to intraperitoneal injection of insulin (0.65 u/kg). c, Fasting serum insulin levels in control and Mac-PPARγ KO mice after 4 hr fast. d, Homa-IR index of insulin sensitivity (insulin [ng/ml] x glucose [mM]). e-f, Decreased insulin signaling in obese Mac-PPARγ KO mice. Control and Mac-PPARγ KO mice were injected with insulin (5 mU/g), and cellular lysates were immunoblotted for total and serine phosphorylated (S473) Akt; liver (e) and quadriceps (f). g-h, Relative transcript levels of genes involved in β-oxidation and oxidative phosphorylation, and of transcriptional regulators controlling these pathways in quadriceps (g) and liver (h). i, Circulating levels of adiponectin in control and Mac-PPARγ KO mice.

Similar articles

Cited by

References

    1. Shoelson SE, Lee J, Goldfine AB. Inflammation and insulin resistance. J Clin Invest. 2006;116:1793–801. - PMC - PubMed
    1. Hotamisligil GS. Inflammation and metabolic disorders. 2006;444:860–867. - PubMed
    1. Weisberg SP, et al. Obesity is associated with macrophage accumulation in adipose tissue. J Clin Invest. 2003;112:1796–808. - PMC - PubMed
    1. Xu H, et al. Chronic inflammation in fat plays a crucial role in the development of obesity-related insulin resistance. J Clin Invest. 2003;112:1821–30. - PMC - PubMed
    1. Kanda H, et al. MCP-1 contributes to macrophage infiltration into adipose tissue, insulin resistance, and hepatic steatosis in obesity. J Clin Invest. 2006;116:1494–505. - PMC - PubMed

Publication types

MeSH terms

Substances

Grants and funding

LinkOut - more resources